Methods of forming copper-based nitride liner/passivation layers for conductive copper structures and the resulting device

ABSTRACT

One illustrative method disclosed herein includes forming a trench/via in a layer of insulating material, forming a barrier layer in the trench/via, forming a copper-based seed layer on the barrier layer, converting at least a portion of the copper-based seed layer into a copper-based nitride layer, depositing a bulk copper-based material on the copper-based nitride layer so as to overfill the trench/via and performing at least one chemical mechanical polishing process to remove excess materials positioned outside of the trench/via to thereby define a copper-based conductive structure. A device disclosed herein includes a layer of insulating material, a copper-based conductive structure positioned in a trench/via within the layer of insulating material and a copper-based silicon or germanium nitride layer positioned between the copper-based conductive structure and the layer of insulating material.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Generally, the present disclosure relates to the manufacture ofsophisticated semiconductor devices, and, more specifically, to variousmethods of forming copper-based nitride liner/passivation layers forcopper-based conductive structures, such as conductive lines/vias, thatare formed on integrated circuit products.

2. Description of the Related Art

The fabrication of advanced integrated circuits, such as CPUs, storagedevices, ASICs (application specific integrated circuits) and the like,requires a large number of circuit elements, such as transistors,capacitors, resistors, etc., to be formed on a given chip area accordingto a specified circuit layout. During the fabrication of complexintegrated circuits using, for instance, MOS (Metal-Oxide-Semiconductor)technology, millions of transistors, e.g., N-channel transistors (NFETs)and/or P-channel transistors (PFETs), are formed on a substrateincluding a crystalline semiconductor layer. A field effect transistor,irrespective of whether an NFET transistor or a PFET transistor isconsidered, typically includes doped source and drain regions that areformed in a semiconducting substrate and separated by a channel region.A gate insulation layer is positioned above the channel region and aconductive gate electrode is positioned above the gate insulation layer.By applying an appropriate voltage to the gate electrode, the channelregion becomes conductive and current is allowed to flow from the sourceregion to the drain region.

In a field effect transistor, the conductivity of the channel region,i.e., the drive current capability of the conductive channel, iscontrolled by a gate electrode formed adjacent to the channel region andseparated therefrom by a thin gate insulation layer. The conductivity ofthe channel region, upon formation of a conductive channel due to theapplication of an appropriate control voltage to the gate electrode,depends on, among other things, the dopant concentration, the mobilityof the charge carriers and, for a given extension of the channel regionin the transistor width direction, the distance between the source anddrain regions, which is also referred to as the channel length of thetransistor. Thus, in modern ultra-high density integrated circuits,device features, like the channel length, have been steadily decreasedin size to enhance the performance of the semiconductor device and theoverall functionality of the circuit. For example, the gate length (thedistance between the source and drain regions) on modern transistordevices has been continuously reduced over the years and further scaling(reduction in size) is anticipated in the future. This ongoing andcontinuing decrease in the channel length of transistor devices hasimproved the operating speed of the transistors and integrated circuitsthat are formed using such transistors. However, there are certainproblems that arise with the ongoing shrinkage of feature sizes that mayat least partially offset the advantages obtained by such feature sizereduction. For example, as the channel length is decreased, the pitchbetween adjacent transistors likewise decreases, thereby increasing thedensity of transistors per unit area. This scaling also limits the sizeof the conductive contact elements and structures, which has the effectof increasing their electrical resistance. In general, the reduction infeature size and increased packing density makes everything more crowdedon modern integrated circuit devices, at both the device level andwithin the various metallization layers.

Improving the functionality and performance capability of variousmetallization systems has also become an important aspect of designingmodern semiconductor devices. One example of such improvements isreflected in the increased use of copper metallization systems inintegrated circuit devices and the use of so-called “low-k” dielectricmaterials (materials having a dielectric constant less than about 3) insuch devices. Copper metallization systems exhibit improved electricalconductivity as compared to, for example, prior metallization systemsthat used tungsten for the conductive lines and vias. The use of low-kdielectric materials tends to improve the signal-to-noise ratio (S/Nratio) by reducing crosstalk as compared to other dielectric materialswith higher dielectric constants. However, the use of such low-kdielectric materials can be problematic as they tend to be lessresistant to metal migration as compared to some other dielectricmaterials.

Copper is a material that is difficult to etch using traditional maskingand etching techniques. Thus, conductive copper structures, e.g.,conductive lines or vias, in modern integrated circuit devices aretypically formed using known single or dual damascene techniques. Ingeneral, the damascene technique involves (1) forming a trench/via in alayer of insulating material, (2) depositing one or more relatively thinbarrier or liner layers (e.g., TiN, Ta, TaN), (3) forming coppermaterial across the substrate and in the trench/via, and (4) performinga chemical mechanical polishing process to remove the excess portions ofthe copper material and the barrier layer(s) positioned outside of thetrench/via to define the final conductive copper structure. The coppermaterial is typically formed by performing an electrochemical copperdeposition process after a thin conductive copper seed layer isdeposited by physical vapor deposition on the barrier layer.

Unfortunately, it is becoming more difficult to satisfy the ongoingdemand for smaller and smaller conductive lines and conductive vias fora variety of reasons. One such problem with traditional barrier layermaterials, e.g., tantalum, tantalum nitride, ruthenium, is the minimumthickness to which those materials must be formed so that they can beformed as continuous layers and perform their intended functions. Thus,having to make the barrier material a certain minimum thickness meansthat there is less room in the trench for the copper material.Accordingly, the overall resistance of the conductive structureincreases, as the barrier layer material is less conductive than copper.Additionally, copper seed layers are typically formed to a thickness ofabout 5 nm to account for a portion of the seed layer will be oxidized,e.g., about 2-3 nm, between the time the copper seed layer is initiallyformed and the actual plating process. The additional thickness requiredfor the copper seed layer also means that there is less room in thetrench, thereby making filling operations more difficult. The presenceof the oxidized seed layer may also lead to undesirable migration ofoxygen in the surrounding structures.

The present disclosure is directed to various methods of formingcopper-based nitride liner/passivation layers for copper-basedconductive structures that may solve or at least reduce some of theproblems identified above.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an exhaustive overview of the invention. It is notintended to identify key or critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome concepts in a simplified form as a prelude to the more detaileddescription that is discussed later.

Generally, the present disclosure is directed to various methods offorming copper-based nitride liner/passivation layers for copper-basedconductive structures that are formed on integrated circuit products.One illustrative method disclosed herein includes forming a trench/viain a layer of insulating material, forming a barrier layer in thetrench/via, forming a copper-based seed layer on the barrier layer,converting at least a portion of the copper-based seed layer into acopper-based nitride layer, depositing a bulk copper-based material onthe copper-based nitride layer so as to overfill the trench/via andperforming at least one chemical mechanical polishing process to removeexcess materials positioned outside of the trench/via to thereby definea copper-based conductive structure.

One illustrative device disclosed herein includes a layer of insulatingmaterial, a copper-based conductive structure positioned in a trench/viawithin the layer of insulating material and a copper-based siliconnitride layer positioned between the copper-based conductive structureand the layer of insulating material.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich like reference numerals identify like elements, and in which:

FIGS. 1A-1J depict various methods disclosed herein of formingcopper-based nitride liner/passivation layers for copper-basedconductive structures, such as conductive lines/vias, that are formed onintegrated circuit products.

While the subject matter disclosed herein is susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and are herein described indetail. It should be understood, however, that the description herein ofspecific embodiments is not intended to limit the invention to theparticular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

Various illustrative embodiments of the invention are described below.In the interest of clarity, not all features of an actual implementationare described in this specification. It will of course be appreciatedthat in the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

The present subject matter will now be described with reference to theattached figures. Various structures, systems and devices areschematically depicted in the drawings for purposes of explanation onlyand so as to not obscure the present disclosure with details that arewell known to those skilled in the art. Nevertheless, the attacheddrawings are included to describe and explain illustrative examples ofthe present disclosure. The words and phrases used herein should beunderstood and interpreted to have a meaning consistent with theunderstanding of those words and phrases by those skilled in therelevant art. No special definition of a term or phrase, i.e., adefinition that is different from the ordinary and customary meaning asunderstood by those skilled in the art, is intended to be implied byconsistent usage of the term or phrase herein. To the extent that a termor phrase is intended to have a special meaning, i.e., a meaning otherthan that understood by skilled artisans, such a special definition willbe expressly set forth in the specification in a definitional mannerthat directly and unequivocally provides the special definition for theterm or phrase.

The present disclosure is directed to various methods of formingcopper-based nitride liner/passivation layers for copper-basedconductive structures, such as conductive lines/vias, that are formed onintegrated circuit products. As will be readily apparent to thoseskilled in the art upon a complete reading of the present application,the present method is applicable to a variety of technologies, e.g.,NFET, PFET, CMOS, etc., and is readily applicable to a variety ofdevices, including, but not limited to, ASIC's, logic devices, memorydevices, etc. With reference to the attached drawings, variousillustrative embodiments of the methods disclosed herein will now bedescribed in more detail.

FIG. 1A is a simplified view of an illustrative integrated circuitdevice 100 at an early stage of manufacturing that is formed above asemiconductor substrate (not shown). The substrate may have a variety ofconfigurations, such as a bulk substrate configuration, an SOIconfiguration, and it may be made of materials other than silicon. Thus,the terms “substrate” or “semiconducting substrate” should be understoodto cover all semiconducting materials and all forms of such materials.The device 100 may be any type of integrated circuit device that employsany type of a conductive copper structure, such as a conductive line orvia commonly found on integrated circuit devices. At the point offabrication depicted in FIG. 1A, a trench/via 14 has been formed in alayer of insulating material 10 by performing known photolithography andetching techniques through a patterned mask layer 12. The trench/via 14is intended to be representative of any type of opening formed in anytype of insulating material 10 wherein a conductive copper structure maybe formed. The trench/via 14 may be of any desired shape, depth orconfiguration. For example, in some embodiments, the trench/via 14 is aclassic trench that does not extend to an underlying layer of material,such as the illustrative trench 14 depicted in FIG. 1A. In otherembodiments, the trench/via 14 may be a through-hole type feature, e.g.,a classic via, that extends all of the way through the layer ofinsulating material 10 and exposes an underlying layer of material or anunderlying conductive structure (not shown), such as an underlying metalline. Thus, the shape, size, depth or configuration of the trench/via 14should not be considered to be a limitation of the present invention.The trench/via 14 may be formed by performing any of a variety ofdifferent etching processes, e.g., a dry reactive ion etching process,through the patterned mask layer 12.

The various components and structures of the device 100 may be initiallyformed using a variety of different materials and by performing avariety of known techniques. For example, the layer of insulatingmaterial 10 may be comprised of any type of insulating material, e.g.,silicon dioxide, a low-k insulating material (k value less than 3),etc., it may be formed to any desired thickness and it may be formed byperforming, for example, a chemical vapor deposition (CVD) process orspin-on deposition (SOD) process, etc. The patterned mask layer 12 maybe formed using known photolithography and/or etching techniques. Thepatterned mask layer 12 is intended to be representative in nature as itcould be comprised of a variety of materials, such as, for example, aphotoresist material, silicon nitride, silicon oxynitride, silicondioxide, a metal, etc. Moreover, the patterned mask layer 12 could becomprised of multiple layers of material, such as, for example, a padoxide layer (not shown) and a pad silicon nitride layer (not shown) thatis formed on the pad oxide layer. Thus, the particular form andcomposition of the patterned mask layer 12 and the manner in which it ismade should not be considered a limitation of the present invention. Inthe case where the patterned mask layer 12 is comprised of one or morehard mask layers, such layers may be formed by performing a variety ofknown processing techniques, such as a CVD process, an atomic layerdeposition (ALD) process, a physical vapor deposition (PVD) process, orplasma enhanced versions of such processes, and the thickness of such alayer(s) may vary depending upon the particular application. In oneillustrative embodiment, the patterned mask layer 12 is a hard masklayer of silicon nitride that is initially formed by performing a CVDprocess to deposit a layer of silicon nitride and thereafter patterningthe layer of silicon nitride using known sidewall image transfertechniques and/or photolithographic techniques combined with performingknown etching techniques.

Next, as shown in FIG. 1B, a deposition process, e.g., a PVD, CVD or ALDprocess, is performed to form a barrier layer 16 across the product 100and in the trench/via 14. The barrier layer 16 may be comprised ofsingle or multiple layers of any of a variety of different materials,e.g., tantalum, cobalt, ruthenium, manganese, tantalum nitride, titaniumnitride, titanium or combinations thereof. The thickness of the barrierlayer 16 may vary depending upon the particular application, e.g., 0.5-3nm.

FIG. 1C depicts the device 100 after a deposition process, e.g., a PVD,CVD or ALD process, is performed to form a copper-based seed layer 18across the product 100 and in the trench/via 14 on the barrier layer 16.The copper-based seed layer 18 may be comprised of substantially purecopper. The thickness of the copper seed layer 18 may vary dependingupon the particular application, e.g., 2-10 nm. The relative sizes ofthe layers 16, 18 to the finished conductive copper-based structure areexaggerated in the attached drawings to facilitate explanation.

Thereafter, as shown in FIG. 1D, a process operation 20 is performed toconvert substantially the entire copper-based seed layer 18 to acopper-based nitride layer 22. In one illustrative embodiment, theprocess operation 20 is a thermal or plasma operation that may beperformed using at least one nitrogen-containing precursor. For example,in one embodiment, the process operation may be performed usingtrigermylamine ((H₃Ge)₃N) or trisilylamine ((H₃Si)₃N) to react with thecopper-based seed layer 18 and thereby form a layer 22 of coppergermanium nitride (Cu_(x)GeN_(y)) or a layer 22 of copper siliconnitride (Cu_(x)SiN_(y)), respectively. In this embodiment, the processoperation may be either a thermal or plasma based process that isperformed at a temperature that falls within the range of about 40-500°C.

In another embodiment of the process operation, germane (GeH₄) or silane(SiH₄), at a flow rate of about 1-100 sccm, may be introduced in aplasma based operation to react with the copper-based seed layer 18. Inthis example, a nitrogen-containing gas, e.g., nitrogen, ammonium, etc.,at a flow rate of about 1-100 sccm, is introduced with the germane orsilane to thereby form the copper-based nitride layer 22 comprised ofcopper germanium nitride (Cu_(x)GeN_(y)) or copper silicon nitride(Cu_(x)SiN_(y)), respectively. The reaction temperature of thisembodiment of the process operation 20 may be on the order of about40-500° C. As compared to the traditional copper seed layer used to formconductive copper structures, the copper-based nitride layer 22functions as a barrier for copper and oxygen and has a much lowerelectrical resistance as compared to commonly employed barrier layerssuch as ruthenium, cobalt, tantalum and tantalum nitride.

In yet another example, after the copper-based seed layer 18 is formed,the process operation 20 involves performing a plasma doping processwhereby nitrogen or ammonia and germanium or silicon (depending upon theapplication) are introduced into the copper-based seed layer 18. Such aplasma doping process may be performed at a temperature within the rangeof about 40-500° C. This plasma treatment process converts thecopper-based seed layer 18 into the copper-based nitride layer 22comprised of copper germanium nitride (Cu_(x)GeN_(y)) or copper siliconnitride (Cu_(x)SiN_(y)), respectively.

In yet another embodiment, the copper-based nitride layer 22 is formedby introducing various materials during the process of forming thecopper-based seed layer 18 using a traditional deposition process usinggermanium or silicon containing materials. In one embodiment, nitrogenor ammonia and germanes of general formula Ge_(n)H_(2n+2) or germaniumtetrahalides may be introduced during the deposition process that isperformed to form the copper-based seed layer 18 to thereby result in alayer of copper germanium nitride (Cu_(x)GeN_(y)) 22. In anotherexample, nitrogen or ammonia and silane (SiH₄) or (Si_(n)H_(2n+2)) orsilicon tetrahalides may be introduced during the deposition processthat is performed to form the copper-based seed layer 18 to therebyresult in a layer of copper silicon nitride (Cu_(x)SiN_(y)) 22.

Next, as shown in FIG. 1E, an appropriate amount of bulk copper-basedmaterial 24, e.g., a layer of copper about 500 nm or so thick, is formedacross the device 100 in an attempt to insure that the trench/via 14 iscompletely filled with copper. In an electroplating process, electrodes(not shown) are coupled to the copper-based nitride layer 22 at theperimeter of the device 100 and a current is passed through thecopper-based nitride layer 22, which causes the bulk copper material 24to deposit and build on the copper-based nitride layer 22. Thecopper-based materials 18, 24 may be comprised of pure copper, or acopper alloy, including, for example, copper-aluminum, copper-cobalt,copper-manganese, copper-magnesium, copper-tin and copper-titanium, withalloy concentration ranging from 0.1 atomic percent to about 50 atomicpercent based on the particular application.

FIG. 1F depicts the device 100 after at least one chemical mechanicalpolishing (CMP) process has been performed to remove excess bulkcopper-based material 24, the copper-based nitride layer 22 and thebarrier layer 16 positioned outside of the trench/via 14 to therebydefine a conductive copper-based structure 26. In this embodiment, thepatterned mask layer 12 is depicted as being removed as part of thepolishing process. In other embodiments, the patterned mask layer 12 mayremain in place above the layer of insulating material 10 and act as apolish-stop layer during the CMP process(es).

FIGS. 1G-IJ depict another illustrative embodiment disclosed herein.FIG. 1G depicts the device 100 at a point of fabrication wherein thebarrier layer 16 and the copper-based seed layer 18 have been formedabove the device 100 as previously described. Next, as shown in FIG. 1H,a process operation 20A is performed to form a relatively thincopper-based nitride layer 22A on the remaining portions of thecopper-based seed layer 18. In one illustrative embodiment, thecopper-based nitride layer 22A may be formed by simply varying theduration and/or temperature of either of the process operationsdescribed above with respect to the formation of the previouslydescribed copper-based nitride layer 22. In one illustrative example,the copper-based nitride layer 22A may have a thickness of about 1-3 nm,and the remaining portions of the copper-based seed layer 18 may have athickness of about 2-7 nm. In effect, in this embodiment, thecopper-based nitride layer 22A acts as a passivation layer for theunderlying copper-based seed layer 18. Thereafter, as shown in FIG. 1I,the bulk copper material 24 was formed as described above. Then, asshown in FIG. 1J, the previously described CMP process(es) was performedto remove excess materials positioned outside of the trench/via 14. Aswill be appreciated by those skilled in the art after a complete readingof the present application, the use of the copper-based nitride layersdisclosed herein may be very beneficial as it relates to the formationof conductive copper structures on integrated circuit devices.

The particular embodiments disclosed above are illustrative only, as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. For example, the process steps set forth above may beperformed in a different order. Furthermore, no limitations are intendedto the details of construction or design herein shown, other than asdescribed in the claims below. It is therefore evident that theparticular embodiments disclosed above may be altered or modified andall such variations are considered within the scope and spirit of theinvention. Accordingly, the protection sought herein is as set forth inthe claims below.

What is claimed:
 1. A method, comprising: forming a trench/via in alayer of insulating material; forming a barrier layer in at least saidtrench/via; forming a copper-based seed layer on said barrier layer;converting at least a portion of a thickness of said copper-based seedlayer into a copper-based nitride layer; depositing a bulk copper-basedmaterial above said copper-based nitride layer so as to overfill saidtrench/via; and performing at least one chemical mechanical polishingprocess to remove excess materials positioned outside of said trench/viato thereby define a copper-based conductive structure.
 2. The method ofclaim 1, wherein converting said at least a portion of a thickness ofsaid copper-based seed layer into said copper-based nitride layercomprises converting substantially an entire thickness of saidcopper-based seed layer into said copper-based nitride layer.
 3. Themethod of claim 1, wherein said copper-based nitride layer is positionedbetween said copper-based conductive structure and said barrier layer.4. The method of claim 1, wherein said barrier layer is comprised of oneof tantalum, tantalum nitride, titanium, titanium nitride, cobalt orruthenium.
 5. The method of claim 1, wherein said copper-based nitridelayer is comprised of one of copper germanium nitride (Cu_(x)GeN_(y)) orcopper silicon nitride (Cu_(x)SiN_(y)).
 6. The method of claim 1,wherein converting said at least a portion of said thickness of saidcopper-based seed layer into said copper-based nitride layer comprisesreacting one of trigermylamine ((H₃Ge)₃N) or trisilylamine ((H₃Si)₃N)with said copper-based seed layer.
 7. The method of claim 6, whereinreacting one of trigermylamine ((H₃Ge)₃N) or trisilylamine ((H₃Si)₃N)with said copper-based seed layer comprises performing one of a thermalor plasma based process that is performed at a temperature that fallswithin the range of about 40-500° C.
 8. The method of claim 1, whereinconverting said at least a portion of said thickness of saidcopper-based seed layer into said copper-based nitride layer comprisesperforming a plasma process in the presence of one of germane (GeH₄) orsilane (SiH₄) and a nitrogen-containing gas.
 9. The method of claim 1,wherein converting said at least a portion of said thickness of saidcopper-based seed layer into said copper-based nitride layer comprisesperforming a plasma doping process whereby germanium or silicon andnitrogen are introduced into said copper-based seed layer.
 10. Themethod of claim 9, wherein said plasma doping process is performed at atemperature that falls within the range of about 40-500° C.
 11. Amethod, comprising: forming a trench/via in a layer of insulatingmaterial; forming a barrier layer in at least said trench/via;performing a copper deposition process to form a copper-based seed layeron said barrier layer; forming a copper-based nitride layer on saidcopper-based seed layer by introducing a germanium-containing gas or asilicon-containing gas and a nitrogen-containing gas during at least aportion of said copper deposition process; depositing a bulkcopper-based material on said copper-based nitride layer so as tooverfill said trench/via; and performing at least one chemicalmechanical polishing process to remove excess materials positionedoutside of said trench/via to thereby define a copper-based conductivestructure.
 12. The method of claim 11, wherein forming said copper-basednitride layer comprises converting substantially an entire thickness ofsaid copper-based seed layer into said copper-based nitride layer. 13.The method of claim 11, wherein said copper-based nitride layer ispositioned between said copper-based conductive structure and saidbarrier layer.
 14. The method of claim 11, wherein said barrier layer iscomprised of one of tantalum, tantalum nitride, titanium, titaniumnitride, cobalt or ruthenium.
 15. The method of claim 11, wherein saidcopper-based nitride layer is comprised of one of copper germaniumnitride (Cu_(x)GeN_(y)) or copper silicon nitride (Cu_(x)SiN_(y)).